import java.util.*;
import java.util.stream.IntStream;

class Solution {
	
	public static void main( String[] args ) {
		// read values with in.next...() methods
		var prices = new Scanner( System.in ).tokens()
				.mapToInt( Integer::valueOf )
				.toArray();
		
		// code your solution here
		var maxSum = IntStream.range( 2, prices.length - 1 )
				.map( sellIndex -> {
					var firstRange = Arrays.copyOfRange( prices, 0, sellIndex );
					var secondRange = Arrays.copyOfRange( prices, sellIndex - 1, prices.length );
					return maxProfit( firstRange ) + maxProfit( secondRange );
				})
				.max().orElse( 0 );
		
		// Write result with System.out.println()
		System.out.println( maxSum );
	}
	
	private static int maxProfit( int[] prices ){
		return IntStream.range( 0, prices.length )
				.map( index -> {
					var range = Arrays.copyOfRange( prices, index, prices.length );
					var max = IntStream.of( range ).max().orElse( 0 );
					// difference between current price and future maximum
					return max - prices[index];
				})
				.max().orElse( 0 );
	}
	
}